1. Technical Field
The present invention relates generally to semiconductor devices, and more particularly, to an interlayer connector for preventing delamination of layers of a semiconductor device, and methods of forming the connector.
2. Related Art
Semiconductor fabricators are increasingly facing challenges relative to delamination of layers within a semiconductor device. One reason for the increased significance of this issue is that the industry is currently turning to the use of lower dielectric constant (low-k) dielectric materials to lower capacitances in the continuous pursuit of smaller semiconductor devices. Some of these low-k dielectric materials include SiLK™ from Dow Chemical, Coral™ from Novellus Systems and Black Diamond™ from Applied Materials. Delamination issues arise relative to these materials because they are extremely difficult to integrate with other materials. For example, it is very difficult to attain good adhesion between interfaces of different materials where the materials include a low-k dielectric. The poor adhesion of the new low-k materials is present relative to other dielectrics and metal. As a result of the poor adhesive properties, widespread use of these materials must overcome the delamination problem. Conventionally, adhesion promoters or treatments have been applied to decrease the likelihood that delamination will occur between interfaces. In cases of some of the newer low-k dielectrics, however, this approach does not work.
Another challenge relative to addressing the low-k dielectric material delamination problem is that the semiconductor industry is currently undecided in terms of which type of material will ultimately be favored. For example, the integrated circuit (IC) industry is pursuing parallel paths regarding use of chemical vapor deposited (CVD) materials such as Coral and Black Diamond, and spin-on dielectrics such as SiLK. Each category of material presents its own problems relative to the adhesion/delamination problem. For example, to lower the dielectric constant of CVD materials, carbon has been substituted in the form of methyl groups (CHx) for oxygen in silicon dioxide. However, the carbon addition creates more adhesion problems, and requires more specialized processing. Other low-k materials may not pose this problem, but present other issues relative to delamination. As a result, addressing the delamination problem is difficult because any solution must address the varying challenges of each low-k material that may eventually find widespread use.
Further delamination problems are presented by back-end-of-line (BEOL) low-k dielectrics that have very high coefficient of thermal expansion (CTE) as compared to the on device wiring and substrate. In particular, the CTE mismatch causes yield and reliability problems as the device or wafer is thermally cycled up and down in temperature. For example, devices are stressed at temperature ranges of approximately −150° C. to +150° C. For dielectrics such as polyarylene ether (i.e., SiLK or Flare™ by Honeywell), the stressing has led to catastrophic device fails during stressing due to poor via to wire resistance after stressing (i.e. via opens). One partial solution to this problem has been to add via fill to the existing white space wire fill used on a device. That is, instead of simple wire fill in the white space, providing vias also. With via fill, white-space-fill wire shapes are connected together by vias to connect the wiring layers together and reduce the CTE mismatch induced expansion and contraction during thermal cycling. See, for example, U.S. Pat. No. 6,559,543 to Dunham et al., and assigned to the assignee of the present application, International Business Machines (IBM). One problem with via fill, however, is that it is only usable when white space wire fill shapes are stacked on top of each other, which only occurs on wiring levels with low wiring density. Another problem with via fill is that they are subject to the same stresses as active vias and can de-adhere form underlying metal. Accordingly, this approach finds limited applicability.
In view of the foregoing, there is a need in the art for an improved mechanism to prevent interlayer delamination that addresses the problems of the related art.